Is there any easier way. I spent ages setting up rulesets to get different articulations happening on my score in Notion 6. Then when I export to Studio One, I have to change it all to articulations via keyswitch notes, as they dont translate across systems. Is there an easier way or is this just what you have to do?

There is a very easy way. In Notion, use File>Send to Studio One, select the option to send Notes, and Notion will automatically export all the notes, the tempo settings (including nTempo settings, if present), the dynamics, any VST instruments and their settings, AND the keyswitches associated with any rules you've used.

Revised something in the Notion score after export? Send it again, and select the option to Merge into Open Document. Notion will resend the data with the changes in place.

I've had limited experience with channel change messages, but the experiments I've tried have failed since Studio One is designed to use only one MIDI channel per track.

I'm not certain about East West; There were presets at one time, but I think the functionality of them was broken at some point. I'd ask the question in a separate post. There are a lot of EW users here.